Enter the morph tunnel then exit G-mode. Shooting the shot block off screen can be done by jumping and shooting up or with Grapple or a Power Bomb. Getting positioned under the shot block can be done by walking into the camera scroll block and then walking against the right wall, jump to the left and walk a little more (about one more tile). This will also give some visibility of Samus. Without heat damage, it is recommended to jump up past the shot block and wait for it to respawn; with the block intact, Samus can't accidentally touch the lava.

Entrance condition:

{
  "comeInWithGMode": {
    "mode": "any",
    "morphed": true
  }
}

Requires:

"h_heatedGMode"
"canOffScreenMovement"
{
  "or": [
    "h_canArtificialMorphMovement",
    {
      "ammo": {
        "type": "PowerBomb",
        "count": 3
      }
    }
  ]
}
{
  "or": [
    "canInsaneJump",
    {
      "and": [
        "canTrickyJump",
        "h_heatProof"
      ]
    },
    {
      "and": [
        "h_heatProof",
        "h_lavaProof",
        {
          "or": [
            "Gravity",
            "HiJump"
          ]
        }
      ]
    }
  ]
}
{
  "heatFrames": 1000
}